The present invention relates to a zoom lens having an illumination system incorporated therein which is used for uses requiring illumination.
In the past, no zoom lens having an illumination system incorporated therein has been available.
Therefore, in the case where illumination is required, illumination lamps or illumination devices 2 are arranged in the vicinity of an object to be observed X, as shown in FIG. 1(a); a ring light device 3 is provided at an end of a zoom lens 1, as shown in FIG. 1(b); or illumination devices 2 are mounted on opposite sides of a zoom lens 1, as shown in FIG. 1(c).
The above-described prior art has problems as follows:
1) The FIG. 1(a) arrangement is inconvenient in that when the zoom lens 1 is moved in order to observe an object to be observed located at a different place, the separate illumination systems also have to be moved.
2) The FIG. 1(b) arrangement does not have the problem encountered in the FIG. 1(a) arrangement, but the operability for the purpose of changing the degree of magnification is poor.
3) The FIG. 1(c) arrangement is inconvenient when used at a short working distance (a distance between a zoom lens and an object to be observed), because the illumination system is larger than the zoom lens or is located externally of a lens frame, and therefore, the illumination system hits the object to be observed or the object to be observed becomes invisible from outside or the object to be observed cannot be manually handled.